I installed “Modeller” using the info on
http://salilab.org/modeller/9v7/release.html#rpm. However I get the
error message “warning modeller9v7-1.x86_64.rmp: Header V4 DSA
signature: NOKEY, Key ID” .
That's fine (like it says, it's a warning, not an error) - it just means
it wasn't able to verify the package's cryptographic signature (so you
have no idea whether the package was tampered with). It installed fine,
however (unless you got some other error messages).